Dosing

Adults (over 18 years old)

Recommended dietary allowances (RDAs) are 2.4 micrograms per day for adults and adolescents aged 14 years and older, 2.6 micrograms per day for adult and adolescent pregnant females, and 2.8 micrograms per day for adult and adolescent lactating females. Because 10-30% of older people do not absorb food-bound vitamin B12 efficiently, those over 50 years of age should meet the RDA by eating foods fortified with B12 or by taking a vitamin B12 supplement. Supplementation of 25-100 micrograms per day has been used to maintain vitamin B12 levels in older people. A doctor and pharmacist should be consulted for use in other indications. Vitamin B12 has been taken by mouth and given by intramuscular (IM) injection by healthcare professionals. One clinical trial tested patients' acceptance of intranasal vitamin B12 replacement therapy (500 micrograms per week).

Children (under 18 years old)

Recommended dietary allowances (RDAs) have not been established for all pediatric age groups; therefore Adequate Intake (AI) levels have been used instead. The RDA and AI of vitamin B12 are: infants 0-6 months, 0.4 micrograms (AI); infants 7-12 months, 0.5 micrograms (AI); children 1-3 years, 0.9 micrograms; children 4-8 years, 1.2 micrograms; and children 9-13 years, 1.8 micrograms.

Safety

DISCLAIMER:
Many complementary techniques are practiced by healthcare professionals with formal training, in accordance with the standards of national organizations. However, this is not universally the case, and adverse effects are possible. Due to limited research, in some cases only limited safety information is available.

Allergies

Vitamin B12 supplements should be avoided in people sensitive or allergic to cobalamin, cobalt, or any other product ingredients.

Side Effects and Warnings

Caution should be used in patients undergoing angioplasty since an intravenous loading dose of folic acid, vitamin B6, and vitamin B12 followed by oral administration taken daily after coronary stenting might actually increase restenosis rates. Due to the potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents.

Itching, rash, transitory exanthema, and urticaria have been reported. Vitamin B12 and pyridoxine has been associated with cases of rosacea fulminans, characterized by intense erythema with nodules, papules, and pustules. Symptoms may persist for up to four months after the supplement is stopped, and may require treatment with systemic corticosteroids and topical therapy.

Diarrhea has been reported.

Peripheral vascular thrombosis has been reported. Treatment of vitamin B12 deficiency can unmask polycythemia vera, which is characterized by an increase in blood volume and the number of red blood cells. The correction of megaloblastic anemia with vitamin B12 can result in fatal hypokalemia and gout in susceptible individuals, and it can obscure folate deficiency in megaloblastic anemia. Caution is warranted.

Vitamin B12 is contraindicated in early Leber's disease, which is hereditary optic nerve atrophy. Vitamin B12 can cause severe and swift optic atrophy.

Pregnancy and Breastfeeding

Vitamin B12 is likely safe when used orally in amounts that do not exceed the recommended dietary allowance (RDA).

There is insufficient reliable information available about the safety of larger amounts of vitamin B12 during pregnancy.